Mostly changes to new unit tests.

Binary blobs containing zeros are now handled correctly.

Protobuf3 needs to be linked into the catalogue command line tools as we
use protobuf format to store checksums inside the DB.

Should be more efficient as it's a single copy operation instead of one
character at-a-time, but still requires 2 copies of the blob to convert
it from occi::Bytes to std::string (as it needs an intermediate char*
array).

It isn't necessary to serialize the protobuf to compute the serialized
length, use ByteSizeLong() instead.

Adds support for byte array columns in the DB. Implementation done for
SQLite, the others are placeholders.